Seed Production Environment and Potential Seed Longevity of Rain-fed Sesame (Sesamum indicum L.) Genotypes
Variability and adaptability of potential seed longevity were investigated in 14 sesame genotypes grown in three plant population environments in South Western Nigeria in each of the two cropping seasons. Seeds obtained from these genotypes were subjected to accelerated aging test using methanol-aging techniques. Data obtained were subjected to analysis of variation and differences, means separation at 5% probability level and stability test. The test genotypes exhibited significant differences in seed longevity in five out of the six environments. Genotype 73A-11 had distinct seed longevity potential in all the environments except in 266,667 plants ha-1. The stability analysis result indicated that regression coefficients ranged from 0.05-2.06 and were statistically close to unit. Four genotypes, 73A-11, 93A-97, E8 and CK2 were desirable with high seed longevity potential in all the environments. Genotype 73A-11, 93A-97, E8 and CK2 were identified as desirable genotypes with potential for high longevity in any of the three plant population densities. The result further identified 73A-11, 93A-97, E8, CK2 and Pbtil as being most appropriate in 133,333 plants ha-1 and all the genotypes except 93A-97, Type A, 530-6-1 and 69B-882 in 166,667 plants ha-1 while all the genotypes except Type A, 530-6-1 would be appropriate in 266,667 plants ha-1. The identified genotypes were superior in seed longevity potential and hence could be considered in commercial seed production and future seed improvement programme.
to cite this article:
M.A. Adebisi, M.O. Ajala and T.O. Kehinde, 2011. Seed Production Environment and Potential Seed Longevity of Rain-fed Sesame (Sesamum indicum L.) Genotypes. Research Journal of Seed Science, 4: 166-173.
Received: January 10, 2011;
Accepted: June 01, 2011;
Published: July 09, 2011
Sesame (Sesamum indicum L.) is an ancient oil crop supplying seeds for
confectionery purposes, edible oil, paste, cake and flour. It is typically a
crop of small farmers in the developing countries. It is adapted to tropical
and temperate conditions, grows well on stored soil moisture with minimal irrigation
or rainfall, can produce good yield under high temperature and its grain has
a high value (Delgado and Yermanos, 1979).
Sesame production areas in Nigeria have remained generally stable over the
years until recently when it was introduced to South-West, Nigeria. Competition
from more remunerative crops, low yield potential, poor filed establishment,
problem of harvesting and high labour cost have pushed sesame to less fertile
fields and to areas of higher risk, if left unchecked, production may decrease
in the foreseeable future. This provides an opportunity to produce larger quantities
of high quality sesame seed to farmers. One aspect of seed performance, which
shows variation, is the seed longevity (Uzoh, 1998).
Wide fluctuation in the seed yield and quality of seed obtainable in sesame
from year to year has been reported by Adebisi et al.
(2003, 2004). As a consequence, target plant population
densities may not be met, even when an appropriate seed rate is used. The fluctuation
can be traced to the use of seed of very poor quality resulting from unfavourable
environmental factors, poor nutrition of mother plant, infection of plant diseases
and the level of plant protection, poor storage life, high deterioration rate
among others (Adebisi et al., 2005).
According to Heydecker (1972), the response of seeds
to any stress will be the representative of their ability to cope with other
stress while the response will differ from one condition to another. Crop genotypes
are known to differ genetically in their stability across environments. An ideal
variety is the one that combines high seed quality with stability of performance
(which is mostly attributable to an acceptable phenotype over a wide range of
environmental conditions (Allard and Bradshaw, 1964).
Stability of seed longevity is of special importance under rain-field conditions
in under-developed countries where environmental conditions vary considerably
and the means of modifying the environment are far from adequate and expensive.
The findings of Adebisi and Ajala (2008) in seed yield
and quality stability proved that the method could efficiently be used to analyse
the responses of different varieties under various conditions. The data may
help in choosing the best genotype for any given environment and cultivation
Therefore, this study was designed to determine the extent of variability and stability of seed longevity in some Nigerian sesame genotypes grown under different plant population densities in the southwest, Nigeria and to identify those genotypes, with high seed longevity potential under such unstable environment.
MATERIALS AND METHODS
Seeds of fourteen sesame genotypes sourced from the National Cereals Research Institute, Badeggi, Niger State, Nigeria, were evaluated in trials conducted at the Teaching and Research Farm of the University of Agriculture, Abeokuta (7° 15'N, 3° 25'E). Seeds of the 14 sesame were grown under three plant populations during the rainy seasons of 2001 and 2002 constituting six environments as follows: Environment 1 = 50-15 cm (133,333 plants ha-1) and Environment 2 = 60-10 cm (166,667 plants ha-1) and Environment 3 = 75-5 cm (266,667 plants ha-1).
The average rainfall for the two seasons ranged from 500 mm annum-1 in 2001 to about 800 mm annum in 2002. At each plant population and in each season, the 14 entries were arranged in randomized complete blocks with three replications. Sowing was done by hand in 4-row plots of 3m long and spaced 50-15, 60-10 and 75-5 cm. Seeds were mixed with sand and hand-dried while seedlings were thinned at three weeks after sowing to about 15, 10 and 5 cm between plants.
Following thinning, a post-emergence fertilizer application of NPK 15:15:15
was applied by drilling at the rate of 60 kg N, 30 kg P2O5
and 50 kg K2O ha-1. Weeding was carried out twice, before
and after fertilizer application. The experimental fields were well-drained
sandy-loamy soil with a pH range of 6.81 to 7.80, N status between 0.07 and
0.14%, organic matter between 1.42 and 2.86% and C status between 0.82 and 1.66%.
Seeds harvested from each of the environments were evaluated in the laboratory
for seed longevity using the procedure outlined by Musgrave
et al. (1980) and Tiwari and Hariprasad, 1997.
Three replicates of 100 seeds each per replicate were placed in a moist bucket
chamber at room temperature for 2 days. Seeds were then soaked in 20% (v/v)
aqueous solutions of methanol for 2 h followed by soaking in distilled water
for 5 min. Seeds were placed in petri dishes for viability count after three
Data analysis: The analysis of variance (three-way ANOVA) was applied using GENSTAT statistical package to estimate and test for significance of year, plant population and genotype effects and first- and second-order interactions.
Stability parameters for each genotype were determined using the regression
procedure of Eberhart and Russell (1966). Each genotype
was defined by three values: (1) mean seed yield over all environments, (2)
the linear regression (b values) of genotype mean seed yield in each environment
and (3) the mean square deviation (S2d value). Significance of regression
coefficient (b values) was tested by the Students t test. For the regression
ANOVA, the residuals from the combined ANOVA were used as a pooled error to
test the significance of the S2d values (Osman,
1991). A significant f-value would indicate that S2d was significantly
different from zero. Co-efficient of determination (R2 values) was
computed from individual linear regression analysis (Pinthus,
RESULTS AND DISCUSSION
From the results in Table 1, the analysis of variance showed
significant difference in seed longevity between plant population densities
and genotypes while the season effect was not significant. The first-order interactions
between population and season, genotype and season and genotype and population
were highly significant revealing that the relative ranking of the sesame for
seed longevity with respect to both plant population density and the season
was not constant. The genotype varied in seed longevity between the seasons
and the plant population density modulated seed longevity of the 14 sesame genotypes.
The presence of second-order interaction of genotypexpopulationxseason indicated
that there were significant changes in population effects over the season on
seed longevity. These findings were in agreement with those of reported by Adebisi
et al. (2008) for sesame seed quality in South West, Nigeria and
(Ezzat et al., 2010) in agronomic performance,
genotypexenvironment interaction and stability analysis of grain sorghum.
The results presented in Table 2 shows that the 14 sesame
genotypes recorded significant variation in seed longevity potential in five
out of the six environments examined. From Table 2, genotype
93A-97, 73A-11 as well as E8 with seed longevity values of 80, 81 and 74%, respectively
was significantly higher at 133,333 plants ha-1 during 2001 season
while 73A-94 (44%) and Domu (49%) were among the genotypes with lower seed longevity
|| Analysis of variance of seed potential longevity of 14 sesame
genotype harvested from six environments
|*, **Significant at 5, 1% level, respectively, ns: Not significant
|| Seed longevity of sesame genotypes grown at three plant population
densities during 2001 and 2002 cropping season
|Means in the same column followed by the same letter are not
significantly different from one another at p<0.05, S1: 2001 cropping
season, S2: 2002 cropping season
During 2002 season, out of 33,333 plants ha-1, two genotypes 93A-57
(76%) and Domu (78%) recorded distinct higher seed longevity whereas Goza (57%),
530-6-1 (59%) was among genotypes with low seed longevity potential. At 166,667
plant ha-1, only genotypes Yandev 55 (81%), 73A-94 (79%), 73A-11
(79%) and C-K-2 (79%) were identified with remarkable and significantly higher
seed longevity in 2001 while Type A (44%) and 530-3 (42%) had low seed longevity
in the same season. However, in 2002, genotypes 73A-97 (78%), followed by Yandev
55 (76%), 73A-11 (75%), 73A-94 (73%) and Domu (73%) had significantly higher
seed longevity potential whereas 530-3 and 93A-57 with 55% values recorded significantly
low seed longevity. Increasing the population to 266,667 plants ha-1,
the variations in seed longevity among the genotypes were not significant in
2001, in 2002. Five genotypes, Yandev 55 (70%), 93A-57 (72%), C-K-2 (71%), Domu
(70%), 69B-88Z (70%), 530-3 (71%), 73A-97(69%) and E8 (67%) had significant
higher seed longevity potential whereas Type A (56%) were among genotypes with
significantly lower seed longevity. A cursory look of the population density
means showed that 2001 season at 266,667 plants ha-1 had higher seed
longevity which may be attributed to a better growth environment characterised
greater solar radiation, good temperature, regular and adequate rainfall and
favourable soil conditions.
Mean seed longevity of 14 sesame genotypes across two cropping seasons across
three plants densities are presented in Table 3. Significant
differences occurred among the genotypes within the cropping season. In 2001
cropping season, genotypes 73A-11 (80%), 93A-57 (78%), followed by E8 (74%),
C-K-2 (73%) recorded significantly greater seed longevity whereas Type A with
58% was identified with low seed longevity potential. Similarly, in 2002 cropping
season, genotypes, Yandev 55 (73%), 73A-11 (73%), Domu (73%), 73A-97 (74%) had
significant higher seed longevity, closely followed by E8 (70%), C-K-2 (71%),)
and 73A-94 (69%) while 530-6-1 (59%) recorded lowest seed longevity. From this
Table 3, genotypes 73A-11, E8 and C-K-2 were identified with
consistent superior seed longevity potential in each of the seasons.
|| Mean potential seed longevity of 14 sesame genotypes under
two cropping seasons across three plant population environment
|Means in the same column followed by the same letter are not
significantly different from at p<0.05, S1: 2001 cropping season, S2:
2002 cropping season
|| Analysis of variance of Finlay-Wilkinson regression of potential
seed longevity of 14 sesame genotypes in six environments
|*, **Significant at 0.05 and 0.01 levels of probability, respectively,
ns: Not significant
These genotypes deserve a better place in future seed improvement strategies.
Hassanpanah (2010) also showed that Agria and Caesar
cultivars had high tuber yield in all sites and for the four different irrigation
regimes for two years in an experiment conducted to determine the yield performance
and stability of three potato cultivars and four irrigation regimes in six environments.
The joint regression analysis revealed that the GxE (Linear) effect due to
environment showed significant differences between regression coefficients pertaining
to the regression of genotype seed longevity on environmental seed longevity.
The result showed that there were differences among slopes of regression lines
and the regression model was adequate in describing the stability of the sesame
genotypes Table 4. Similar findings were earlier reported
by Osman (1991) and Adebisi (2010)
for seed yield of rain-fed sesame and seed quality (germination and field emergence)
of sesame. Also, Tiawari et al. (2011) reported
similar result in GenotypexEnvironment interaction and stability analysis in
elite clones of sugarcane.
Mean seed longevity and estimates of stability parameters in 14 sesame genotypes
at six environments are shown in Table 4. Since the environment
sum of squares contributed to the regression sum of squares, Adebisi
and Ajala (2008) reported that linear regression accounted for 84-99, 7-82
and 0-89% of the variations in seed yields, seed germination and field emergence
of sesame, respectively.
|| Mean potential seed longevity and estimates of stability
parameters in 14 sesame genotypes at six environments
|Means in the same column followed by the same letter are not
significantly different from one another at p<0.05. *, **significant
at 0.05 and 0.01 levels of probability, ns: Not significant. R2:
Coefficient of determination, S2d: Mean square deviation from
regression, T: t test value, Fwb: Finlay-Wilkinson regression
According to Eberhart and Russell (1966), a genotype
considered stable should meet the criteria of high mean seed longevity with
b equal to unit and S2d approaching zero. Using these criteria, one
genotype 73A-97 with regression coefficient of 1.00, S2d approaching
zero and with relatively high mean seed longevity (Table 5)
could be considered widely adapted and stable and with ability to express longevity
potential in an array of environmental conditions. This supports earlier findings
by Osmanzai and Sharma (2008) for high yielding stable
wheat genotypes for diverse environments in Afghanistan.
A desirable genotype is one with high mean, at least average performance in
all environments and an undesirable genotype or below average performance in
some environments. Following Choo et al. (1984)
criteria and defining high mean seed longevity performance as at least 5% above
the grand mean, only genotypes 73A-11, 93A-57, E8 and C-K-2 showed themselves
to be desirable in all cropping seasons and plant density environments (Table
5). In 2003, Min and Saleh (2003) also reported
Suwan 1 as the best performer for 100-grain weight among the 14 grain maize
genotypes selected for stability performance in four different locations thus
revealing average stability of the genotype.
Similarly, performance at individual plant density (Table 6) revealed that 73A-11, E8, 73A-97 and C-K-2 recorded above average longevity in each of the three plant densities examined in this study. Among these genotypes, only 73A-11, E8 and C-K-2 as indicated previously appeared to be the most desirable. It may thus be concluded that the regression analysis effectively identified 73A-97, 73A-11, E8 and C-K-2 as desirable genotypes that will give high seed longevity across an array of environments encountered in the south-west of Nigeria and similar rain-fed ecologies. However, when applied to individual plant density environment, the method used pointed out 93A-57, 73A-11, E8, 73A-97, C-K-2 and Pbtil as being most appropriate for cultivation in 133, 333 plants ha-1 and all the genotypes except 93A-57, Type A, 530-61 and 69B-88Z in 166,667 plants ha-1 and all the genotypes except Type A and 530-6-1 would be most suitable for cultivation in 266,667 plants ha-1 environments.
|| Mean potential seed longevity under three plant population
environments across two cropping seasons
The test genotypes showed considerable variations in potential seed longevity and were sensitive to factors limiting seed quality; hence their wider adaptability, stability and general performance to the fluctuations in the growing conditions within and across cropping seasons and plant density environments were considerably lowered. The stability analysis provides meaningful stability and consistency of performance of rain-fed sesame genotypes across different environments.
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